Cleaning the troughs must be peformed daily, in the morning and evening. A thin board nearly as wide as the trough and shaped like a hand shovel, is made with a short stick for a handle nailed across it. When this is held in the water across the trough it creates a strong current under it. It is held in the left hand while in the right hand is a small brush broom such as is used in cleaning sinks, and with which the sides and bottom of the trough are well scrubbed. All the dirt is sucked under the board and carried along to the lower end of the trough. The fish are also crowded together ahead of the cleaning operation and out of the way of the broom. When the lower part is reached the fry are driven above and the operation completed by netting out the larger pieces of meat or dirt, and by rubbing the finer partieles through the screen at the lower end of the trough; or, a high cross bar may be put in, the screen raised for a moment and the waste plug opened.

When there is not accommodation in the troughs for all the fry and they can not be distributed, a temporary place of retention may be made by using the shad boxes which are described under the chapter on shad hatching. These need not generally be set at an angle to the current, as the mere ordinary disturbance of the water near the outlet of the ponds will give them motion enough to change the water. These will only answer temporarily and must be cleaned as carefully as the troughs. They are to be scrubbed all over the inside and on the bottom. To do this without injuring the fish, the box is tipped up so as to bring one part after the other out of the water where it can be brushed, while the fry are safely swimming at the other end.

If the fry must be kept in confinement, absolute cleanliness is a necessary prerequisite to their health ; but we can not too strongly impress upon our readers the desirability of turning them out into the small rivulets connected with the waters where they are to live, as soon as possible after the sac is absorbed. Although they encounter some perils to which they are not exposed if kept in preserves, they escape still more dangers and acquire the habit of taking care of themselves which is necessary when they come finally to be thrown upon their own resources.

Food

The best food for trout fry is raw liver, chopped as fine as possible, and then rubbed through a screen or sieve with a flat stick. It must be reduced to the consistency of pulp, and contain no strings or gristle. A chopping machine is made for chopping hash and sausage, and either that, or a couple of sharp knives are used to chop the liver. What is used is mixed with water so as to reduce it to about the thickness of cream. A teacup full of this mixture will feed a hundred thousand fish when they first begin to feed. The best way to feed them is to take a case-knife, dip it in the food and shirt off what adheres into the troughs; a very simple way, but one answering all practical purposes. Care should be taken not to feed too much, else the surplus food will remain on the bottom, and decaying there foul the trough. The reason of the difficulty in raising young fish appears to be that they are literally starved to death. The food which we can give them is not natural to them, it is often given in such coarse pieces that they cannot take it, and sometimes, through the carelessness of a hired hand, they are neglected two or three days at a time.

It is impossible to get the natural food for the fry, in fact no one knows what it is, further than that it must be microscopic insects of some sort, as the adult trout are never known to feed on anything but animal food. It is found in the spring runs, even actually in them, as they apparently issue bare of life from the bosom of the earth. Liver is but a poor and unnatural substitute for this food with fish so delicate as the trout, and if they once get the habit of feeding naturally on what the water offers they will not take the artificial food afterward. Fish, of any age, learn to eat that food which is most abundant around them. Anglers know this by experience, and use the flies which they see on the stream on which they are fish ing. It is supposed that a trout is very fond of grasshoppers, but the trout in one of our ponds which we have fed for a long time with beef lights, will not look at grasshoppers, and will turn up their noses at the fattest and juiciest worms, while the trout fresh caught out of the stream, which we have put in a pond by themselves to educate, will for weeks refuse the daintiest bits of lights and liver. Hunger will after a time drive them to change their food; but with the young ones we cannot wait for this, as they will die off before they learn. As the fish grow older and stronger more food must be given to them ; when six months old, a bowl full of liver will answer for a thousand. While the fish are young, feed often; six or eight times a day for the first two or three months; three times a day will do after three months until they are a year old.

Young salmon, young salmon trout, California mountain trout, and above all young California salmon are larger, have stronger appetite, and will accept coarser food. For them, although at first the liver should be made as fine as for trout when they are a few weeks old, it will be hardly necessary to dilute it at all, and in the course of a few months they will not only take the larger pieces, often tearing them apart, but will scorn the finer portion. At one time sour milk was almost exclusively used for feeding young fish, but it has been given up. Other foods have been tried, but with no better success. The fish will not thrive on any of them as well as they do on liver, and do not thrive on that as well as if it were a natural food.

As they grow older, other things may be substituted or may be added to it as a change. They are fond of the roe of other fish, of the spawn of the horse-foot or king-crab; of fish itself, and when they are large enough to eat minnows, no better food can be given them. Liver is too expensive when it has to be used alone for grown fish, and beef lights are usually added to it or used in place of it in a measure. It is miserable food however, much of it passing through the stomachs of the trout and salmon wholly undigested and collecting in the bottom of the ponds. It injures the digestive organs and must be deleterious to the health of the fish. Its only recommendation is that it is cheap. Maggots are bred on spoilt meat, hung over the ponds, and as they fall off and drop into the water are readily devoured, and make excellent food. Or a piece of spoilt meat may be placed in a deep bottle like a preserving bottle, and the flies that will collect in immense numbers during summer may be caught and emptied into the water. This trap will take many times its bulk of flies by being kept set all the time and emptied when any one is passing it. Flies are probably the best food that can be given to trout.

One difficulty with all this family of fish which is accustomed to seize its prey while in motion, is that they will very rarely pick up food from the bottom. To obviate this, a plan of keeping the food in motion has been carried out on a small scale by utilizing an invention made at the New York state works for hatching the eggs, called the Holton hatching box, which will be described more fully hereafter. The idea of this was to introduce the water from below and carry it over the top. A funnel shaped tin or wooden vessel is made with the apex below, the water entering this creates a current that prevents the particles of food from descending, and keeps them in motion. Credit for this application of the invention is due to Mr. Winans of Baltimore, but it is at best but partially successful, as the food soon becomes so washed by the water that the fish will reject it, even if they have taken it into their mouths,